#4 Add Session Browser functionality

[randolf_geist]

Initial basic Session Browser should cover the following:

- Grouping of Sessions by arbitrary attribute (e.g. STATUS (ACTIVE/INACTIVE), PROGRAM, USERNAME etc.)
- Automatically group Parallel Slave processes
- Show current SQL
- Show actual execution plan for current SQL, taken from V$SQL_PLAN, or if not available via EXPLAIN PLAN

Advanced features could include:
- Current Session Wait Events
- Session Longops
- Session active Workareas
...